I had Iphotos and I upgrade to catalina, how i can upgrade to Photos?

Photos for Mac is preinstalled as a part of Catalina. Look for it in the Applications folder. The icon looks like a flower in rainbow colors.

Double-click Photos while holding down the options key ⌥. When the dialog to select a library appears, relate the options key.

Then select your iPhoto Library to create a Photos Library from the iPhoto Library.

See: Updating from iPhoto to Photos for OS X - Apple Support

More background information: Notes on Migrating an iPhoto Library from… - Apple Community

Open it from the Applications folder or the Dock.

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